A sniper is completely powerless against tanks, vehicles, and helicopters. Therefore, it should always be covered by other infantry. A sniper can completely decimate any infantry, so make good use of it if there are a lot of infantry on the battlefield. Try to put snipers in forests rather than buildings, because there's always a chance that a sniper in a building is in a wrong window; but if you find a building with two vacant spots (or squares) put either an Infantry squad or AT squad (depending on what you are fighting, tanks, choppers etc.) and put the sniper in as well so he has backup.

The sniper is completely helpless against other vehicles, tanks, and helicopters. It is advised that you call in tactical aid. If you don't have enough TA, then just try to run away and hope that you make it far enough.

Due to its vulnerable nature, snipers are rarely seen in multiplayer, unless their opponent has a lot of infantry squads. If you spot an enemy sniper, it's usually covered by other units such as Light Tanks.